// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef URL_GURL_H_
#define URL_GURL_H_

#include <stddef.h>

#include <iosfwd>
#include <memory>
#include <string>

#include "base/strings/string16.h"
#include "base/strings/string_piece.h"
#include "url/third_party/mozilla/url_parse.h"
#include "url/url_canon.h"
#include "url/url_canon_stdstring.h"
#include "url/url_constants.h"
#include "url/url_export.h"

// Represents a URL.
//
// A parsed canonicalized URL will be guaranteed UTF-8. Only the ref (if
// specified) can be non-ASCII, the host, path, etc. will be guaranteed ASCII
// and any non-ASCII characters will be encoded and % escaped.
//
// The string representation of a URL is called the spec(). Getting the
// spec will assert if the URL is invalid to help protect against malicious
// URLs. If you want the "best effort" canonicalization of an invalid URL, you
// can use possibly_invalid_spec(). Test validity with is_valid(). Data and
// javascript URLs use GetContent() to extract the data.
//
// This class has existence checkers and getters for the various components of
// a URL. Existence is different than being nonempty. "http://www.google.com/?"
// has a query that just happens to be empty, and has_query() will return true
// while the query getters will return the empty string.
//
// Prefer not to modify a URL using string operations (though sometimes this is
// unavoidable). Instead, use ReplaceComponents which can replace or delete
// multiple parts of a URL in one step, doesn't re-canonicalize unchanged
// sections, and avoids some screw-ups. An example is creating a URL with a
// path that contains a literal '#'. Using string concatenation will generate a
// URL with a truncated path and a reference fragment, while ReplaceComponents
// will know to escape this and produce the desired result.
class URL_EXPORT GURL {
public:
    typedef url::StringPieceReplacements<std::string> Replacements;
    typedef url::StringPieceReplacements<base::string16> ReplacementsW;

    // Creates an empty, invalid URL.
    GURL();

    // Copy construction is relatively inexpensive, with most of the time going
    // to reallocating the string. It does not re-parse.
    GURL(const GURL& other);
    GURL(GURL&& other)
    noexcept;

    // The strings to this contructor should be UTF-8 / UTF-16.
    explicit GURL(base::StringPiece url_string);
    explicit GURL(base::StringPiece16 url_string);

    // Constructor for URLs that have already been parsed and canonicalized. This
    // is used for conversions from KURL, for example. The caller must supply all
    // information associated with the URL, which must be correct and consistent.
    GURL(const char* canonical_spec,
        size_t canonical_spec_len,
        const url::Parsed& parsed,
        bool is_valid);
    // Notice that we take the canonical_spec by value so that we can convert
    // from WebURL without copying the string. When we call this constructor
    // we pass in a temporary std::string, which lets the compiler skip the
    // copy and just move the std::string into the function argument. In the
    // implementation, we use std::move to move the data into the GURL itself,
    // which means we end up with zero copies.
    GURL(std::string canonical_spec, const url::Parsed& parsed, bool is_valid);

    ~GURL();

    GURL& operator=(const GURL& other);
    GURL& operator=(GURL&& other);

    // Returns true when this object represents a valid parsed URL. When not
    // valid, other functions will still succeed, but you will not get canonical
    // data out in the format you may be expecting. Instead, we keep something
    // "reasonable looking" so that the user can see how it's busted if
    // displayed to them.
    bool is_valid() const
    {
        return is_valid_;
    }

    // Returns true if the URL is zero-length. Note that empty URLs are also
    // invalid, and is_valid() will return false for them. This is provided
    // because some users may want to treat the empty case differently.
    bool is_empty() const
    {
        return spec_.empty();
    }

    // Returns the raw spec, i.e., the full text of the URL, in canonical UTF-8,
    // if the URL is valid. If the URL is not valid, this will assert and return
    // the empty string (for safety in release builds, to keep them from being
    // misused which might be a security problem).
    //
    // The URL will be ASCII except the reference fragment, which may be UTF-8.
    // It is guaranteed to be valid UTF-8.
    //
    // The exception is for empty() URLs (which are !is_valid()) but this will
    // return the empty string without asserting.
    //
    // Used invalid_spec() below to get the unusable spec of an invalid URL. This
    // separation is designed to prevent errors that may cause security problems
    // that could result from the mistaken use of an invalid URL.
    const std::string& spec() const;

    // Returns the potentially invalid spec for a the URL. This spec MUST NOT be
    // modified or sent over the network. It is designed to be displayed in error
    // messages to the user, as the appearance of the spec may explain the error.
    // If the spec is valid, the valid spec will be returned.
    //
    // The returned string is guaranteed to be valid UTF-8.
    const std::string& possibly_invalid_spec() const
    {
        return spec_;
    }

    // Getter for the raw parsed structure. This allows callers to locate parts
    // of the URL within the spec themselves. Most callers should consider using
    // the individual component getters below.
    //
    // The returned parsed structure will reference into the raw spec, which may
    // or may not be valid. If you are using this to index into the spec, BE
    // SURE YOU ARE USING possibly_invalid_spec() to get the spec, and that you
    // don't do anything "important" with invalid specs.
    const url::Parsed& parsed_for_possibly_invalid_spec() const
    {
        return parsed_;
    }

    // Allows GURL to used as a key in STL (for example, a std::set or std::map).
    bool operator<(const GURL& other) const;
    bool operator>(const GURL& other) const;

    // Resolves a URL that's possibly relative to this object's URL, and returns
    // it. Absolute URLs are also handled according to the rules of URLs on web
    // pages.
    //
    // It may be impossible to resolve the URLs properly. If the input is not
    // "standard" (IsStandard() == false) and the input looks relative, we can't
    // resolve it. In these cases, the result will be an empty, invalid GURL.
    //
    // The result may also be a nonempty, invalid URL if the input has some kind
    // of encoding error. In these cases, we will try to construct a "good" URL
    // that may have meaning to the user, but it will be marked invalid.
    //
    // It is an error to resolve a URL relative to an invalid URL. The result
    // will be the empty URL.
    GURL Resolve(const std::string& relative) const;
    GURL Resolve(const base::string16& relative) const;

    // Creates a new GURL by replacing the current URL's components with the
    // supplied versions. See the Replacements class in url_canon.h for more.
    //
    // These are not particularly quick, so avoid doing mutations when possible.
    // Prefer the 8-bit version when possible.
    //
    // It is an error to replace components of an invalid URL. The result will
    // be the empty URL.
    //
    // Note that we use the more general url::Replacements type to give
    // callers extra flexibility rather than our override.
    GURL ReplaceComponents(const url::Replacements<char>& replacements) const;
    GURL ReplaceComponents(
        const url::Replacements<base::char16>& replacements) const;

    // A helper function that is equivalent to replacing the path with a slash
    // and clearing out everything after that. We sometimes need to know just the
    // scheme and the authority. If this URL is not a standard URL (it doesn't
    // have the regular authority and path sections), then the result will be
    // an empty, invalid GURL. Note that this *does* work for file: URLs, which
    // some callers may want to filter out before calling this.
    //
    // It is an error to get an empty path on an invalid URL. The result
    // will be the empty URL.
    GURL GetWithEmptyPath() const;

    // A helper function to return a GURL containing just the scheme, host,
    // and port from a URL. Equivalent to clearing any username and password,
    // replacing the path with a slash, and clearing everything after that. If
    // this URL is not a standard URL, then the result will be an empty,
    // invalid GURL. If the URL has neither username nor password, this
    // degenerates to GetWithEmptyPath().
    //
    // It is an error to get the origin of an invalid URL. The result
    // will be the empty URL.
    GURL GetOrigin() const;

    // A helper function to return a GURL stripped from the elements that are not
    // supposed to be sent as HTTP referrer: username, password and ref fragment.
    // For invalid URLs or URLs that no valid referrers, an empty URL will be
    // returned.
    GURL GetAsReferrer() const;

    // Returns true if the scheme for the current URL is a known "standard-format"
    // scheme. A standard-format scheme adheres to what RFC 3986 calls "generic
    // URI syntax" (https://tools.ietf.org/html/rfc3986#section-3). This includes
    // file: and filesystem:, which some callers may want to filter out explicitly
    // by calling SchemeIsFile[System].
    bool IsStandard() const;

    // Returns true when the url is of the form about:blank, about:blank?foo or
    // about:blank/#foo.
    bool IsAboutBlank() const;

    // Returns true if the given parameter (should be lower-case ASCII to match
    // the canonicalized scheme) is the scheme for this URL. Do not include a
    // colon.
    bool SchemeIs(base::StringPiece lower_ascii_scheme) const;

    // Returns true if the scheme is "http" or "https".
    bool SchemeIsHTTPOrHTTPS() const;

    // Returns true if the scheme is valid for use as a referrer.
    bool SchemeIsValidForReferrer() const;

    // Returns true is the scheme is "ws" or "wss".
    bool SchemeIsWSOrWSS() const;

    // We often need to know if this is a file URL. File URLs are "standard", but
    // are often treated separately by some programs.
    bool SchemeIsFile() const
    {
        return SchemeIs(url::kFileScheme);
    }

    // FileSystem URLs need to be treated differently in some cases.
    bool SchemeIsFileSystem() const
    {
        return SchemeIs(url::kFileSystemScheme);
    }

    // Returns true if the scheme indicates a network connection that uses TLS or
    // some other cryptographic protocol (e.g. QUIC) for security.
    //
    // This function is a not a complete test of whether or not an origin's code
    // is minimally trustworthy. For that, see Chromium's |IsOriginSecure| for a
    // higher-level and more complete semantics. See that function's documentation
    // for more detail.
    bool SchemeIsCryptographic() const
    {
        return SchemeIs(url::kHttpsScheme) || SchemeIs(url::kWssScheme) || SchemeIs(url::kHttpsSuboriginScheme);
    }

    // Returns true if the scheme is "blob".
    bool SchemeIsBlob() const
    {
        return SchemeIs(url::kBlobScheme);
    }

    // Returns true if the scheme indicates a serialized suborigin.
    bool SchemeIsSuborigin() const
    {
        return SchemeIs(url::kHttpSuboriginScheme) || SchemeIs(url::kHttpsSuboriginScheme);
    }

    // The "content" of the URL is everything after the scheme (skipping the
    // scheme delimiting colon). It is an error to get the content of an invalid
    // URL: the result will be an empty string.
    std::string GetContent() const;

    // Returns true if the hostname is an IP address. Note: this function isn't
    // as cheap as a simple getter because it re-parses the hostname to verify.
    bool HostIsIPAddress() const;

    // Not including the colon. If you are comparing schemes, prefer SchemeIs.
    bool has_scheme() const
    {
        return parsed_.scheme.len >= 0;
    }
    std::string scheme() const
    {
        return ComponentString(parsed_.scheme);
    }
    base::StringPiece scheme_piece() const
    {
        return ComponentStringPiece(parsed_.scheme);
    }

    bool has_username() const
    {
        return parsed_.username.len >= 0;
    }
    std::string username() const
    {
        return ComponentString(parsed_.username);
    }
    base::StringPiece username_piece() const
    {
        return ComponentStringPiece(parsed_.username);
    }

    bool has_password() const
    {
        return parsed_.password.len >= 0;
    }
    std::string password() const
    {
        return ComponentString(parsed_.password);
    }
    base::StringPiece password_piece() const
    {
        return ComponentStringPiece(parsed_.password);
    }

    // The host may be a hostname, an IPv4 address, or an IPv6 literal surrounded
    // by square brackets, like "[2001:db8::1]". To exclude these brackets, use
    // HostNoBrackets() below.
    bool has_host() const
    {
        // Note that hosts are special, absence of host means length 0.
        return parsed_.host.len > 0;
    }
    std::string host() const
    {
        return ComponentString(parsed_.host);
    }
    base::StringPiece host_piece() const
    {
        return ComponentStringPiece(parsed_.host);
    }

    // The port if one is explicitly specified. Most callers will want IntPort()
    // or EffectiveIntPort() instead of these. The getters will not include the
    // ':'.
    bool has_port() const
    {
        return parsed_.port.len >= 0;
    }
    std::string port() const
    {
        return ComponentString(parsed_.port);
    }
    base::StringPiece port_piece() const
    {
        return ComponentStringPiece(parsed_.port);
    }

    // Including first slash following host, up to the query. The URL
    // "http://www.google.com/" has a path of "/".
    bool has_path() const
    {
        return parsed_.path.len >= 0;
    }
    std::string path() const
    {
        return ComponentString(parsed_.path);
    }
    base::StringPiece path_piece() const
    {
        return ComponentStringPiece(parsed_.path);
    }

    // Stuff following '?' up to the ref. The getters will not include the '?'.
    bool has_query() const
    {
        return parsed_.query.len >= 0;
    }
    std::string query() const
    {
        return ComponentString(parsed_.query);
    }
    base::StringPiece query_piece() const
    {
        return ComponentStringPiece(parsed_.query);
    }

    // Stuff following '#' to the end of the string. This will be UTF-8 encoded
    // (not necessarily ASCII). The getters will not include the '#'.
    bool has_ref() const
    {
        return parsed_.ref.len >= 0;
    }
    std::string ref() const
    {
        return ComponentString(parsed_.ref);
    }
    base::StringPiece ref_piece() const
    {
        return ComponentStringPiece(parsed_.ref);
    }

    // Returns a parsed version of the port. Can also be any of the special
    // values defined in Parsed for ExtractPort.
    int IntPort() const;

    // Returns the port number of the URL, or the default port number.
    // If the scheme has no concept of port (or unknown default) returns
    // PORT_UNSPECIFIED.
    int EffectiveIntPort() const;

    // Extracts the filename portion of the path and returns it. The filename
    // is everything after the last slash in the path. This may be empty.
    std::string ExtractFileName() const;

    // Returns the path that should be sent to the server. This is the path,
    // parameter, and query portions of the URL. It is guaranteed to be ASCII.
    std::string PathForRequest() const;

    // Returns the host, excluding the square brackets surrounding IPv6 address
    // literals. This can be useful for passing to getaddrinfo().
    std::string HostNoBrackets() const;

    // Returns true if this URL's host matches or is in the same domain as
    // the given input string. For example, if the hostname of the URL is
    // "www.google.com", this will return true for "com", "google.com", and
    // "www.google.com".
    //
    // The input domain should be lower-case ASCII to match the canonicalized
    // scheme. This call is more efficient than getting the host and check
    // whether host has the specific domain or not because no copies or
    // object constructions are done.
    bool DomainIs(base::StringPiece lower_ascii_domain) const;

    // Checks whether or not two URLs are differing only in the ref (the part
    // after the # character).
    bool EqualsIgnoringRef(const GURL& other) const;

    // Swaps the contents of this GURL object with |other|, without doing
    // any memory allocations.
    void Swap(GURL* other);

    // Returns a reference to a singleton empty GURL. This object is for callers
    // who return references but don't have anything to return in some cases.
    // If you just want an empty URL for normal use, prefer GURL(). This function
    // may be called from any thread.
    static const GURL& EmptyGURL();

    // Returns the inner URL of a nested URL (currently only non-null for
    // filesystem URLs).
    //
    // TODO(mmenke): inner_url().spec() currently returns the same value as
    // caling spec() on the GURL itself. This should be fixed.
    // See https://crbug.com/619596
    const GURL* inner_url() const
    {
        return inner_url_.get();
    }

    // Estimates dynamic memory usage.
    // See base/trace_event/memory_usage_estimator.h for more info.
    size_t EstimateMemoryUsage() const;

private:
    // Variant of the string parsing constructor that allows the caller to elect
    // retain trailing whitespace, if any, on the passed URL spec, but only if
    // the scheme is one that allows trailing whitespace. The primary use-case is
    // for data: URLs. In most cases, you want to use the single parameter
    // constructor above.
    enum RetainWhiteSpaceSelector { RETAIN_TRAILING_PATH_WHITEPACE };
    GURL(const std::string& url_string, RetainWhiteSpaceSelector);

    template <typename STR>
    void InitCanonical(base::BasicStringPiece<STR> input_spec,
        bool trim_path_end);

    void InitializeFromCanonicalSpec();

    // Returns the substring of the input identified by the given component.
    std::string ComponentString(const url::Component& comp) const
    {
        if (comp.len <= 0)
            return std::string();
        return std::string(spec_, comp.begin, comp.len);
    }
    base::StringPiece ComponentStringPiece(const url::Component& comp) const
    {
        if (comp.len <= 0)
            return base::StringPiece();
        return base::StringPiece(&spec_[comp.begin], comp.len);
    }

    // The actual text of the URL, in canonical ASCII form.
    std::string spec_;

    // Set when the given URL is valid. Otherwise, we may still have a spec and
    // components, but they may not identify valid resources (for example, an
    // invalid port number, invalid characters in the scheme, etc.).
    bool is_valid_;

    // Identified components of the canonical spec.
    url::Parsed parsed_;

    // Used for nested schemes [currently only filesystem:].
    std::unique_ptr<GURL> inner_url_;
};

// Stream operator so GURL can be used in assertion statements.
URL_EXPORT std::ostream& operator<<(std::ostream& out, const GURL& url);

URL_EXPORT bool operator==(const GURL& x, const GURL& y);
URL_EXPORT bool operator!=(const GURL& x, const GURL& y);

// Equality operator for comparing raw spec_. This should be used in place of
// url == GURL(spec) where |spec| is known (i.e. constants). This is to prevent
// needlessly re-parsing |spec| into a temporary GURL.
URL_EXPORT bool operator==(const GURL& x, const base::StringPiece& spec);
URL_EXPORT bool operator!=(const GURL& x, const base::StringPiece& spec);

#endif // URL_GURL_H_
